Apparatus for wood chip digestion



0d. 28,, 1958 L. G. DURANT mm. 2,858,211

APPARATUS FOR WOOD CHIP DIGESTION Filed Feb. 15, 1956 2 Sheets$heet 2 FIGB.

INVENTQRAY Leonard G. Durant BY James E. Irvine Rohe V. P'nmngton Alphon se Surino 2,358,21 l Patented Oct. 28, 1958 APPARATUS FOR WOOD CHIP DIGESTIDN Leonard G. Durant, James E. Irvine, Rohe V. Pennington, and Alphonse Surino, Pittsfield, Mass assignors to Coudi Engineering Corporation, Pittsfield, Mass a corporation of- Massachusetts Application February 13,1956, Serial No. 564,987 4 Claims. (Cl. 92-7) This invention relates tothe continuous digestion of cellulosic material such as wood-chips formaking them into pulp. A currentnew type of such digestion treats a downwardly moving column of chips in a primary enclosed vessel or tank wherein thechips are first steamed and then immersed in a pond of cooking liquor with which the chips are then impregnated. The chips are next evacuated from the vessel to a pipe wherein they are diluted with cooking liquor to a controllable pumpable consistency and are immediately pumped to a drainer station wherein they are passed to a secondary vessel wherein again as a downwardly moving column of chips they are digested in non-submergence' onlyin their absorbed and adsorbed liquor. When their digestion is completed, chips are evacuated from the digester and ejected from the system for subsequent treatment. This invention is directed tothe construction and operation of the evacuator means usable both to evacuate impregnated chips from the bottom of the column thereof in the primary vessel and from the bottom of the column thereof in the secondary vessel or digester.

The time of transit of the chips as a column thereof in through each vessel must be carefully controlled automatically, and to that end the level of the columnof chips in each vessel must be maintained substantially constant. In other words, the chips at the bottom of the column thereof in the vessel must be continually removed from the vessel while an equal amount of new chips is supplied to the top of the column thereof. It is not easy to remove chips from the bottom of such a massive column thereof, especially when they are under pressure and high temperature as they are in this system, so it is an object of this invention to devise ways and means for so doing that are highly dependable, simple, cheap, and substantially trouble-free. There must be no tendency for the chips to arch and there must be no possibility for them to channel to the outlet whereby some chips are discharged from the column thereof while others are not. In other words, there must be strictly sequential and uniform discharge of the chips from the column thereof.

To that end, there is provided a central vertical chipevacuation outlet in the bottom of the tank or vessel, upwardly through which rises a motor-driven shaft on which upper end is carried substantially radially extending arms from which depend blades inclined to their path of travel so thatas the blades are moved in circular paths by movement of the arms, the blades rake or plow or sweep chips with which they come into contact, toward the central discharge outlet, while the arms carry a shroud greater in diameter than the discharge outlet, and aligned therewith. The shroud is secured to the arms to move therewith. It has a conical top cover and a depending skirt, but the skirt has at least one port-like opening through which can pass chips plowed toward the skirt by the moving blades. Chips that pass through the port then fall downthe central chip discharge outlet. Thechips in the column thereof with which the blades contact offer significant resistance, so the blades may have. to be properly reinforced. The blade-bearing shaft can be operated by a variable speed motor so that a chip-level controller in either a precedent or in a subsequent station may regulate the rate of discharge of chips by the evacuator mechanism.

The invention is illustrated in the accompanying drawings in which Figure 1 is a somewhat diagrammatic side elevation, with parts in section, of a continuous digestion plant or system that forms the environment of the invention. Fig. 2 is a partial isometric view of a detail of the manifold used to. inject either steam or liquor or both into the vessels. Fig. 3 is a partial vertical sectional view through the bottom of vessel C in Fig. 1, showing details ofthe evacuator mechanism of this invention. Fig. 4, is a partial plan view of the showing of Fig. 3, while Fig. 5, is' a side elevational view. looking toward the left of Fig. 3.

Referring now to Figs: 1 and 2 showing the system there is a chip-bin A for receiving chips, or other cellulosic material to be treated, having an arch-breaker 11, and a suitable rotary chip-discharging mechanism 12. operated by a variable-speed motor-driven mechanism 13, passes chips downward through the feed. pipe 14 at a regulatable rate to a multivane chip feeding mechanism B for delivering chips through pipe 15, valved as at 16 to andinto a primary cylindrical tank or vessel C divided by a liquid-level L into an upper steaming, zone D having a steam atmosphere 17 and a lower impregnating zone E made up of a pond of cooking liquor 18. In the bottom of tank C (sometimes called the impregnator vessel) there is an evacuator mechanismv F for accomplishing continuousdischarge of. chips from the column thereof in the tank by means of a motor mechanism 19 driving a shaft 20, that rotates blade-bearing arms 21 extending radially from a skirt-bearing shroud 22 whose skirt has a port or opening23 therein through which chips are passed downwardly through pipe 24 into pump 25 that forces the chips while submerged in cooking liquor up through delivery conduit 26 to deliver them tangentially to a drainer station G that comprises an inclined enclosed tank 27 having a steam dome 28 with an annular bottom 29 from which uprising a stack 30 down which fall chips and liquor fed tangentially to the steam dome 28 by the delivery conduit 26. The chips and liquor swirl upwardly to spill over the upper weir-like edge ofthe stack 30, but meanwhile tramp metal or other detritus gravitates to the annular bottom 29 from which it can be removed through hand-hole cover 31. Above the bottom of the inclined tank 27, there is a tubular trough 32 having perforations 33, and rotatable in the trough 32 is a screw conveyor 34. Thus chips and liquor descending through stack 30 enter trough 32 up which the screw conveyor 34 moves them meanwhile their liquor drains from them through the perforations 33 and flows from the tank through outlet 35 and pipe 36 for recovery treatment such as in accumulator tank J. The chips that are so drained of the cooking liquor but while retaining their absorbed and adsorbed liquor pass downwardly through pipe 37, valved as at 38, into digestion tank or zone H, where the chips are digested in non-submergence but in the presence of steam and their own adsorbed and absorbed liquor. After being properly digested, they are removed from the digester tank or Zone H by another evacuator mechanism F by means of a motor mechanism 19' driving a shaft 20, that rotates blade-bearing arms 21 extending radially from a shroud 22 having an opening 23' therein through which chips are passed downwardly through pipe 24.. But here pipe 24' leads into an axial flow ejector station I, from whence through pipes 39 and 40 digested chips are blown by a steam stream to further treatment such as into a blow tank from which they go to refining or any other desired treatment. Since it usually becomes important to reclaim and otherwise control the cooking liquor used, I indicates an accumulator tank or station. Cooking liquor of controlled strength is pumped by pump 47 from that tank I through suitably valved liquor inlet line 41 to a conventional automatic valve 42 controlled and regulated by a differential pressure type recording controller 43 for regulating the elevation of the liquid-level L of the pond 18 of cooking liquor so that it is maintained constant, or at least as nearly so as possible. So the automatic valve 42 regulates the flow of liquor through pipe 44 and its branches, each of which lead to an annular manifold 45 having injection nozzles such as 46 extending therefrom into the tank C, whereby liquor can be sprayed into the tank in a fairly dispersed or distributed manner. The manifolds 45 are distributed along the tank C as may seem desirable. Anther pipe 49 also leads from the accumulator tank I and goes to and into the pipe 24 for giving control of the quantity of liquor mixed with the chips discharged from tank C by evacuator F to make them pumpable (at a consistency of say by pump up through pipe 26 to the drainer station G. Still another pipe 48 is used to lead from the top of the accumulator tank I upwardly to the steam dome 28 of the drainer station G. Other valved pipes leading into the accumulator tank I are for conducting certain incoming chemical-bearing liquids thereinto.

From any suitable source, steam under pressure is supplied through steam inlet line 50 to the steaming zone D in the primary tank C by means of an annular manifold 145 in all respects like manifold 45 and having the same kind of injection nozzles 46 to supply steam into the tank in a well distributed manner. The inlet of steam into the manifold 145 is controlled and regulated by a conventional pressure-temperature recording controller 51, that also controls and regulates valve 52 in vaporoutflow line 53. And a final control is indicated generally at 55 that is a chip level gauge and controller that consists of a transmitter containing a radio-active material and a receiver is connected electrically to the motor-drive 13 of chip bin discharger 12, to automatically regulate the chip level to be substantially constant. The instrument is so mounted that the set point can be raised or lowered such as by pulley 56 by the operator.

A similar chip-level sensing gauge and controller 55 is applied to the digester zone or tank H, with its raising and lowering pulley 56 but in this case the controller 55 is connected to and regulates the motor drive 19 on the evacuator station F on the primary vessel C.

Digester zone or station H is' provided with a steaminlet line 58, for delivering steam under pressure to the branch lines 59 and 60 each respectively feeding steam to an annular manifold 245 having injection nozzles, patterned after manifold 45 and its nozzles 46. Inlet of steam through line 58 is controlled and regulated by a conventional pressure-temperature recording controller 61 (similar to controller 51) operating on automatic valve 62 and also an automatic valve 63 includedv in vapor outflow line 64. Valved vapor outlet pipe 65 from the steam dome 28 of the drainer station G, and also from valved vapor outlet pipe 66 from the high point of the inclined tank 27 of that station, can all join into a common exhaust line 67 leading to further treatment of the vapors, if desired, such as for turpentine recovery.

The continuous digestion of cellulosic material such as wood chips carried out by this system in successive treatment zones may be said to comprise feeding chips continuously to the steaming zone where while in columnar formation they are prepared for the ready acceptance of the cooking liquor by appropriate steaming, thus releasing non-condensable gases and otherwise preparing the chips for ready acceptance of the cooking liquor; next submerging the thus conditionsd chips in hot cooking liquor under controlled conditions of time and temperature that assure complete penetration and diffusion of the liquor into the chips but limit the chemical reaction therebetween so that in this zone of impregnating treatment, there is minimized any fiber-degrading action; the chips themselves now contain an amount of absorbed and adsorbed liquor of controlled chemical concentration suflicient to be cooked rapidly but insufficient to cause cellulose degradation, so they are transferred while in submergence and still under pressure from the impregnation zone to a drainage zone where they are relieved of their excess liquor which drains freely therefrom; the drained chips are then cooked also while in columnar formation in only their retained liquor and in non-submergence in a gaseous environment enclosed in a digester; after being cooked, the chips are evacuated from the digester into an ejection zone having a receiver for the digested chips, from whence they are ejected while in suspension in steam and projected or blown to a place of subsequent treatment. All of the action steps are carefully controlled as to pressure, temperature, and the rate of downward movement or the time of transit of the chips through each treatment zone and between such zones, which is a reason why the chip level is maintained substantially constant in each of the vessels C and H; the liquid-level L in vessel C is also so maintained; and the temperature and pressure of the steam is also carefully automatically controlled.

In Fig. 3, the bottom portion of the primary vessel C is shown having a bottom 83 provided with a chip discharge bottom central outlet 84, delivering to a pipe 24 that leads past a valve to a centrifugal pump 25 suitably driven from a motor through a belt 86. The pump forcibly delivers chips immersed in their liquor post valve 37 into pipe through which the chips are pumped up and into the drainer station G. To facilitate this by having sufficient liquor associated with the chips, liquor from the accumulator I is or can be pumped through pipe 49 into the pipe 24. Shaft 20 driven by motor 19 rises upwardly in pipe 24 through an appropriate packing gland 68 to be liquid and steam tight, whereupon the upper end of the shaft reaches into the vessel C sufficient to have bolted to its end a separable coupling 69 from which radially extends two arms 21, from one of which depend a plurality of chip-raking or plowing blades 70, 71 and 72, while from the other depends similar blades 70' and 71'. These blades are inclined toward their path of movement so that they rake or plow or push chips toward the central outlet 84. Since the chips at the bottom of the column thereof offer considerable resistance, the blades each have a, reinforcing strip or rib 73. Depending from the arms 21, in alignment with the outlet 84 is a cylindrical skirt or skirted member 74, slightly less in diameter than the outlet, and secured to the underside of the arms 21 by brackets 75. The skirt has an opening or port 76 in its periphery through which chips can pass, as shown by the arrows in Figs. 3 and 4, which opening or port 76 corresponds to 23 in Fig. 1, except here is shown in greater detail. Above the skirt are two triangular plates 78 and 79 secured to the upper side of the arms 21 and also to the coupling 69, to the top of which is bolted by bolts 80, a conical canopy or cover 81, which combination of canopy and skirt is referred to generally herein as shroud 22 that shields the chip-discharge outlet pipe 24. 82 indicates generally the bracket members used for the support of the various elements. Blade 72 is peculiarly disposed, as can be seen from Fig. 4, so that it guides chips directed into the port-like opening 76 through the skirt 74. The construction of the evacuator station F just described applies with equal force to the evacuator station F in the bottom of the digester vessel H, wherein the evacuator elements have been given primed numerals.

In the evacuator mechanism F shown at the bottom of impregnator vessel C has its motor mechanism 19 a variable speed one, whose speed is regulatably controlled by or from the chip-level sensing and control mechanism 55, which also regulatably controls the speed of the variable speed motor drive 13 for feeding the chips. This is so that that control mechanism can also maintain the column of chips being treated in the digester vessel H at constant height. In other words, if the column of chips in the digester gets too high, the motor 19 of the evacuator mechanism F in the impregnate-r vessel C will be slowed down until the desired or normal height of the column of chips has been restored. On the other hand, if the top of the column gets too low, the evacuator motor 19 will be speeded up.

So in such an assembly or system, a problem to be solved was to devise an evacuator mechanism that would meet all these requirements, and especially to evacuate chips while in columnar formation within a tall tank longitudinally through which the column moved from top to bottom yet which column was fed by individual chips at the top and from the bottom of which individual chips were discharged.

In operation, therefore, rotation of the shaft 20 by the motor mechanism 19, through coupling 69 moves the radial arms 21 through a circular path, and this in turn carries the depending blades 70, 7t), 71, 71, and 72 through circular paths. Movement of these blades dislodges individual chips from the bottom region of the column thereof in the treatment vessel, and movement of the angularly disposed blades pushes or slides the chips inwardly toward the port-like opening 76 in the skirt 74 of the shroud 22. The specially angled blade 72 finally squeezes the chips through that opening whereupon they fall down pipe 24 to discharge into pump 25 if the evacuator is in impregnator vessel C or into the ejector station I, if the evacuator is in digester vessel H. The shroud prevents channelling of chips to the outlet since the cover 81 prevents channelling from above while the skirt 74 prevents channelling from a lateral direction. Since the shroud 22 with its canopy 81 and skirt 74 rotates unitarily with the bladed arms 21, chips enter through the moving door 76 in an orderly and sequential manner.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims and all changes that fall Within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

We claim:

1. Continuously operable wood-chip digesting apparatus which comprises a system having a combined steaming and impregnating tank enclosed for holding a pond of cooking liquor overlain by a steam atmosphere and having a central bottom outlet, means for regulatably supplying steam to the tank, means for regulatably feeding chips to the steam atmosphere, means for feeding such liquor to the pond, means for maintaining a constant liquidlevel on the pond, means for evacuating chips from the tank, a chip drainer, means ;-:'or regulating the passing to the drainer of evacuated impregnated chips immersed in liquor, a chip digester under pressure enclosing a steam atmosphere and having a central bottom outlet, means for regulatahly passing chips from the drainer to the digester, means for supplying steam to the digester for controlling its temperature, means for evacuating chips from the digester, and means for ejecting evacuated digested chips from the system; wherein the evacuating means comprises a motor-driven rotatable shaft extending upwardly through the central bottom outlet, radial arms extending from the shaft movable in a circular path,

lades depending from the arms angled to their paths of movement for pushing chips toward the outlet, and channeliiu eventing shroud means supported from the arms and having a port through which chips pushed thereto by the blades can pass to the outlet.

2. Apparatus according to claim 1, wherein the shroud means comprise a conical canopy surrounding a cylindrical skirted member having a port in its periphery.

3. Apparatus according to claim 2, wherein the canopy is supported from the arms by means of two triangular plates.

4. Apparatus for the continuous digestion of wood chips under heat and pressure, including an enclosed tank having a central bottom outlet, means for feeding chips to the top of the tank to establish a column of such chips extending in the tanl; from bottom to top, means for supplying chip-treatment substances to the tank, and means for evacuating chips from the bottom of the column therein in the tank through the central bottom outlet of the tank including a motor-driven rotatabie shaft extending upwardly through the central bottom outlet, arms eX- tending laterally from the shaft movable in a circular path within the tank, blades depending from the arms angled to their paths of movement for pushing chips in the bottom of the column thereof toward the outlet, and means for minimizing channeling of the chips for shielding the bottom outlet while rotated by and with the blade-bearing arms having a canopy-covered skirt provided with a moving port for radial passage of the blade-pushed chips therethrough to the outlet.

References Cited in the file of this patent UNITED STATES PATENTS 1,521,232 Daae Dec. 30, 1924 2,072,086 De la Roza Mar. 2, 1937 2,200,034 Merrill May 7, 1940 2,289,612 Wells July 14, 1942 2,342,225 Schnyder Feb. 22, 1944 2,474,862 Richter July 5, 1949 2,680,683 Obenshain June 8, 1954 2,717,536 Clark et a1 Sept. 13, 1955 FOREIGN PATENTS 458,863 Great Britain Dec. 29, 1936 134,809 Switzerland NOV. 1, 1929 

1. CONTINUOUSLY OPERABLE WOOD-CHIP DIGESTING APPARATUS WHICH COMPRISES A SYSTEM HAVING A COMBINED STEAMING AND IMPREGNATING TANK ENCLOSED FOR HOLDING A POND OF COOKING LIQUOR OVERLAIN BY A STEAM ATMOSPHERE AND HAVING A CENTRAL BOTTOM OUTLET, MEANS FOR REGULATABLY SUPPLYING STEAM TO THE TANK, MEANS FOR REGULATABLY FEEDING CHIPS TO THE STEAM ATMOSPHERE, MEANS FOR FEEDING SUCH LIQUOR TO THE POND, MEANS FOR MAINTAINING A CONSTANT LIQUIDLEVEL ON THE POND, MEANS FOR EVACUATING CHIPS FROM THE TANK, A CHIP DRAINER, MEANS FOR REGULATING THE PASSING TO THE DRAINER OF EVACUATED IMPREGNATED CHIPS IMMERSED IN LIQUOR, A CHIP DIGESTER UNDER PRESSURE ENCLOSING A STEAM ATMOSPHERE AND HAVING A CENTRAL BOTTOM OUTLET MEANS FOR REGULATABLY PASSING CHIPS FROM THE DRAINER TO THE DIGESTER, MEANS FOR SUPPLYING STEAM TO THE DIGESTER FOR CONTROLLING ITS TEMPERATURE, MEANS FOR EVACUATING CHIPS FROM THE DIGESTER, AND MEANS FOR EJECTING EVACUATED DIGESTED CHIPS FROM THE SYSTEM, WHEREIN THE EVACUATING MEANS 